Pyridoxine hydrochloride

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 October-5 November 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The study was conducted according to OECD Guidelines and in compliance with GLP principles. Although no details are included in the report on analytical validation, the method is deemed sufficiently validated as documented in the report of the Daphnia magna acute toxicity test (Ciba 928379, reliable with restrictions based on lack of detailed method validation results). The reviewer could recalculate the algae growth inhibition from the reported cell densities.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

1984

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Composite samples (about 150 mL per concentration and control) of each test concentration were drawn by mixing identical volumes of the test solutions taken from the approximate center of the test vessels. They were taken immediately before exposure and after 72 hours exposure and kept at - 18 ºC to - 22 ºC until analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: calculated amounts of the stock solution (100 mg test substance with 1000 mL water) to produce the desired test concentrations were homogeneously distributed into the water. The solutions were homogenuous at all test times and test concentrations.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: SAG 86.81
- Source: Collection of algae cultures, Pflanzenphysiologisches Institut, University, Nikolausberger Weg 18, D-3400 Gottingen, Germany
- Age of inoculum (at test initiation): no information; initial cell density is 9400 cells/mL
- Method of cultivation: according to the guideline

ACCLIMATION
- Acclimation period: 3 days
- Culturing media and conditions: same as test

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

No information

Test temperature:

23 ± 1 ºC

pH:

Conc nominal mg/L pH 0 h pH 72h
Blank 7.9 8.3
1.23 7.8 8.4
3.7 7.8 8.4
11 7.7 8.3
33 7.3 8.2
100 6.3 7.3

Dissolved oxygen:

No information

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal: 1.23, 3.7, 11, 33 and 100 mg/L
Measured values: see the table below. Measured values matched the nominal values at the start of the test, but decreased by more than 20 % at the end of the test. The report calculated the effect concentrations on measured end test concentrations (0.4, 1.2, 3.6, 13.9 and 57.1 mg/L, resp). This is deemed extremely conservative. Calculated geometric mean concentrations are more appropiate in case of decreasing test concentrations with time. The reviewer recalculated the measured test concentrations as geometric mean concentrations to be 0.69, 2.1, 6.3, 21.5 and 74.6 mg/L, resp.

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL Erlenmeyer flasks, stoppered with aluminium caps, on Lab-shaker
- Initial cells density: 9400 cells/mL
- Control end cells density: 207 E+4 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes, report states that the composition of the water is according to the guideline.

OTHER TEST CONDITIONS
- Adjustment of pH: not stated
- Photoperiod: Continuous
- Light intensity and quality: cold white fluorescent light, 117 µE/m^2 sec (approx. 8000 lux)

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: TOA cell counter at 24, 48 and 72 hrs

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3
- Range finding study: conducted but not reported

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

72 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

3.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

Only 0-72 h EbC50 and NOEbC values were reported (5.3 mg/L and 1.2 mg/L, respectively, based on measured end concentrations).
The reviewer re-calculated the effect values based on growth rate related to geometric mean measured concentrations.

Results with reference substance (positive control):

None

Reported statistics and error estimates:

Linear regression analysis was performed. For growth rate, R^2 was determined to be 0.92

The cell concentration in the control cultures was increased by a factor of 220 in 3 days, which is > 16 and thus validates the criterium from the OECD 201 (1984). The reviewer calculated the mean coefficient of variation of the daily growth rates in the control to be 6%. The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures was 1%. Therefore, the criteria from the OECD 201 (2006) were also validated.

Validity criteria fulfilled:

yes

Conclusions:

The 72h-ErC50 and ErC10 were calculated to be 72 and 3.3 mg/L, resp. based on geometric mean measured concentrations.

Executive summary:

In a 72h acute toxicity study conducted according to OECD 201, green algae ( Scenedesmus subspicatus) were exposed to Pyridoxin-HCl under static conditions at the following nominal concentrations: blank-control, 1.23, 3.7, 11, 33 and 100 mg/L. Test substance induced 10 and 50 % growth inhibition at 3.3 and 72 mg/L, respectively. These values based on growth rate were recalculated by the reviewer from the raw data and were based on geometric mean measured concentrations. Although no details were included in the report on analytical validation, the method is deemed sufficiently validated in the report of the Daphnia magna acute toxicity test (Ciba 928379, reliable with restrictions based on lack of detailed method validation results). The study is therefore considered to be also reliable with restrictions.

Description of key information

In a 72h acute toxicity study conducted according to OECD 201, green algae (Scenedesmus subspicatus) were exposed to Pyridoxin-HCl under static conditions at the following nominal concentrations: blank-control,1.23, 3.7, 11, 33 and 100 mg/L. Test substance induced 10 and 50 % growth inhibition at 3.3 and 72 mg/L, respectively. These values based on growth rate were recalculated by the reviewer from the raw data and were based on geometric mean measured concentrations. Although no details were included in the report on analytical validation, the method is deemed sufficiently validated in the report of the Daphnia magna acute toxicity test (Ciba 928379, reliable with restrictions based on lack of detailed method validation results).The study is therefore considered to be also reliable with restrictions.

Key value for chemical safety assessment

EC50 for freshwater algae:

72 mg/L

EC10 or NOEC for freshwater algae:

3.3 mg/L